Numerous situations exist in which a body cavity needs to be catheterized to achieve a desired medical goal. One relatively common situation is to provide nutritional solutions or medicines directly into the stomach or intestines. A stoma is formed in the stomach or intestinal wall and a tube is placed through the stoma. This surgical opening and/or the procedure to create the opening is common referred to as “gastrostomy”. Feeding solutions can be injected through the tube (i.e., a feeding tube) to provide nutrients directly to the stomach or intestines in a procedure generally known as enteral feeding. A variety of different feeding tubes intended for enteral feeding have been developed over the years. These devices are frequently referred to as “gastrostomy tubes”, “percutaneous gastrostomy catheters”, “PEG tubes”, “enteral feeding tubes” or “enteral feeding catheters”.
To prevent the PEG tube from being pulled out of the stomach/intestinal wall, various types of retainers are used at a distal end of the catheter. Examples of conventional devices with Malecot tips or similar expanding tips are found at, for example, U.S. Pat. No. 3,915,171 for “Gastrostomy Tube” issued to Shermeta; U.S. Pat. No. 4,315,513 for “Gastrostomy and Other Percutaneous Transport Tubes” issued to Nawash et al.; U.S. Pat. No. 4,944,732 for “Gastrostomy Port” issued to Russo; and U.S. Pat. No. 5,484,420 for “Retention Bolsters for Percutaneous Catheters” issued to Russo. Exemplary commercial products include the Passport® Low Profile Gastrostomy Device available from Cook Medical, Inc. of Bloomington, Ind. and the Mini One™ Non-Balloon Button available from Applied Medical Technology, Inc. of Brecksville, Ohio. A shortcoming of these devices relates to the manner of insertion and withdrawal of a tube incorporating these retaining fixtures (e.g., a gastrostomy tube) into a body lumen such as into the stomach.
Feeding tubes that are initially placed during the gastrostomy procedure have non-inflatable bumpers, bolsters, Malecot tips or similar expanding tips made of a resilient material.
These devices are passed through esophagus of a patient and into the stomach or intestinal space. The narrow tube end of the device is pulled through the stoma and the bolster or bumper which is much larger than the stoma is retained in the stomach or intestinal space to prevent the device from falling out. It is generally thought that the non-inflatable bumper or bolster helps the stoma site heal properly and form a desired shape.
If the feeding tube having the non-inflatable retainer needs to be replaced, it is frequently replaced with a feeding tube that employs an inflatable balloon as the retainer. The balloon, typically made of a “soft” or elastomeric medical grade silicone, is attached to the end of the catheter and is deflated for insertion through the stoma and then inflated to hold the enteral feeding assembly in position. While these balloons have many advantages, these balloons generally provide a much lower level of retention or resistance to being pulled out through the stoma. The balloons generally take on a spherical shape when inflated. Physicians frequently overinflate these balloons to attempt to reduce the radius of curvature of the balloon at the stoma site. That is, a spherical balloon having a larger diameter will tend to have a slightly flatter profile along an arc having a fixed distance in comparison to a spherical balloon having a smaller diameter. The silicone readily deforms while inflated in response to pulling force and may form a funnel or cone shape that helps it travel through the stoma. Elastomeric or “soft” medical grade silicone has a tendency to “creep” or stress relax over time which can change the dimensions of the balloon. In addition, the thickness of these balloons can make it more difficult to insert and remove an uninflated balloon through the stoma. For example, the thickness of a wall of such a silicone balloon typically ranges from about 300 to over 500 micrometers per wall so that the balloon will increase the diameter of the tube to which it is attached by 600 micrometer to over 1000 micrometers (over 1 millimeter).
One attempt to provide a silicone balloon having a non-spherical shape is described in U.S. Patent Application Publication No. 2004/0106899 published Jun. 3, 2004 for a “Gastric Balloon Catheter with Improved Balloon Orientation”. This publication describes a silicone balloon that is molded, pre-shaped or preformed using non-uniformly thick material or expansion limiters so that upon inflation, the silicone expands radially in a non-uniform manner. However, such devices have unsatisfactory thickness in the region of the balloon that makes it difficult to insert the device through a stoma.
Relatively large changes in pressure are needed to stretch such elastic materials from an unstretched state to expand the balloon. Moreover, the relationship between the amount of pressure needed to stretch such elastic materials to expand the balloon and the volume of the balloon is nonlinear. That is, the correlation between the pressure of the fluid inside the balloon and the volume of the balloon is not simple. For example, FIG. 1A is an illustration of a conventional enteral feeding tube device 10 having a base 12 and retainer balloon 13 made of conventional “soft” or elastomeric medical grade silicone in an un-stretched state (i.e., uninflated condition). FIG. 1B is an illustration of a conventional enteral feeding tube device 10 having a base 12 and retainer balloon 13 made of conventional “soft” or elastomeric medical grade silicone which has been stretched by inflation to an inflated volume. FIG. 1C is an illustration showing an exemplary relationship between the pressure of a fluid inside such an elastic retainer balloon and the balloon volume during the stretching the conventional “soft” or elastomeric medical grade silicone forming the balloon by increasing the pressure of a fluid inside the balloon. The illustration is a pressure versus volume plot for a Kimberly-Clark® MIC-KEY® 12 French low profile gastrostomy feeding tube with a conventional silicone balloon. As can be seen in FIG. 1C, stretching such elastic balloons from negligible volume (i.e., a deflated condition) at negligible pressure to a deployed volume between about 3 to about 5 milliliters requires an initially large and continuous change in pressure to overcome the resistance to stretching. In this example, an immediate pressure change from zero or negligible pressure to between about 4 to 7 pounds per square inch (28 to 48 kilopascals) is needed to overcome the resistance to stretching needed to inflate such exemplary conventional retainer balloons to a volume of even 1 cubic centimeter (approximately 1 milliliter) and a pressure between about 5 to 10 pounds per square inch (34 to 69 kilopascals) to inflate such conventional “soft” or elastomeric medical grade silicone balloons to a volume of about 3 cubic centimeters (˜3 milliliters) with sterile water—although saline solution or air can be used.
Accordingly, there is a need for an improved inflatable retention system for an enteral feeding tube having a base deployed outside the human body and an indwelling retainer which is deployed within a lumen of the body by insertion through a stoma from outside the body. A need exists for a retention system utilizing a balloon that has a collapsed, non-inflated state such that the feeding tube and the thin, flexible walls of the balloon can pass through an orifice that is about the same size as the external diameter of the feeding tube. There is also a need for an inflatable retention system that works well and has a stable shape at relatively low pressures (e.g., 4 pounds per square inch (28 kilopascals) or less). There is also a need for an inflatable retention system that provides a level of retention or resistance to being pulled through a stoma that is equal to or better than non-inflatable retention systems. There is also a need for an enteral feeding tube assembly that incorporates such an inflatable retention system.